The England captain Alastair Cook stretches his back during a training session at a suburban cricket ground near Perth. Photograph: Greg Wood/AFP/Getty Images

Matt Prior will lead England in the first warm-up game of their Ashes tour, against a Western Australia Chairman's XI, after Alastair Cook missed practice for the second day running with a stiff back.

England remain relaxed about the latest flare-up of Cook's condition, which has troubled him from time to time over the last few years, and are confident he will be fit to lead the team in next week's game against a much stronger Australia A team in Hobart.

But his absence has forced them to revise their pre-tour strategy. They were already planning to rest Stuart Broad, Graeme Swann and Kevin Pietersen from the three-day game, which starts on Thursday, against a cobbled-together Chairman's XI. Jonny Bairstow, Tim Bresnan and Monty Panesar will also be missing.

Now Michael Carberry will open with Joe Root, giving the Hampshire left-hander the chance to stake a claim for a place in the first Test in Brisbane, which could allow Root to drop back down the order to No6.

Gary Ballance will also have a chance to impress, having been given first crack ahead of Bairstow, and Jimmy Anderson will lead a four-man pace attack in which he will be considerably the shortest, looking up to the three beanpoles Steve Finn, Chris Tremlett and Boyd Rankin.